Proximal Ir-Ir Cooperativity for Reprogramming the CO₂-to-DMF Hydrogenation Pathway

The hydrogenation of CO₂ to N,N-dimethylformamide (DMF) with dimethylamine requires the concerted transformation of three distinct substrates, a fundamental kinetic challenge that mononuclear catalysts can only address through high-barrier, sequential steps. Herein, we demonstrate a ligand-enabled proximity strategy in binuclear Cp*Ir(III) complexes, wherein the spatial confinement of two metal centers facilitates the concerted activation of multiple substrates. The optimized binuclear architecture, equipped with strategically positioned ‒OH pendants, transforms the rate-limiting termolecular collision into a kinetically favorable, low-barrier pathway. This electronic and spatial cooperativity culminates in a turnover number of 1 540 000, placing the catalyst among the most efficient molecular systems reported for DMF production with selectivity approaching quantitative (> 99%). Integrated computational and spectroscopic studies reveal that the dual-Ir framework mitigates the entropic penalty inherent to termolecular processes, while the hydroxyl functionality polarizes the Ir‒H bond to promote H₂ heterolysis and CO₂ insertion. In situ NMR and infrared spectroscopy directly identify the key Ir-hydride and Ir-formate intermediates, providing experimental validation of the computationally predicted low-barrier pathway. These findings establish for the first time how multimetallic cooperativity and secondary coordination sphere effects operate in concert to bypass the intrinsic kinetic limitations of single-site catalysts.